electrical test 3

the term field pole is synonymous with the word stator

false

A motor is a rotating machine that converts mechanical energy into electrical energy

false

there is only one way to class different types of motors: ac or dc

false

brushes carry the current that makes motors spin; therefore, unplug the power cord before changing brushes

true

the nameplate on a motor contains information such as rated voltage and frequency

true

a squirrel cage rotor serves as the core for an induction motor but not a synchronous motor

false

many dc motors work on the concept of using unlike poles to repel one another to spin the armature

true

slip is the difference between the magnetic field of the stator and that of the trailing rotor

true

there is no current flow in the rotor of a squirrel cage motor if it is turning at the same speed as the stator's synchronous field

true

the speed of a synchronous motor can be varied within a given range by adjusting the resistance of the starting resistor connected to the rotor

false

the three phase induction motor operates at synchronous speeds

false

it is possible for CEMF to be produced if the armature is not turning

false

torque can be produced by a motor when its shaft is not turning

true

a motor producing without the shaft turning, performs no usable work

true

the stator flux of a permanent magnet motor is reduced when the rpm is increased due to CEMF

false

arcing between brushes and the commutator is a disadvantage of all ac motors

false

which is not true about a graticule?

voltage is read on the horizontal axis

the letters RMS in electrical terms stand for_____

root mean square

in electrical terms, one complete rotation of a coil inside a magnetic field will___

produce a sinewave

the amplitude of a sine wave at any point in time ______

is its height above and below the reference line(zero) at any given time

the speed of a synchronous motor is regulated by___

the frequency generated by the VFD

a motor that has a magnetic field stator "locked onto" the rotor so they turn at the same speed is called a(n) ____ motor

synchronous

induction motors

dont use coils of wire in their rotor

in the shading coil of the shaded pole motor, the direction of the induced current ____ the magnetic field of the main coil to get the rotor start turning

is shifted from

if a single phase motor hums and does not turn after power is applied, the most likely problem is _______

the start winding is open

the starting torque of a split phase induction motor is maximum when the current through the start and run coils are_______ degrees apart

90

which type of single phase induction motor is used for hard starting applications, such as for compressors

capacitor start

a universal motor operates like a ____ motor when DC power is supplied

series

when the physical load driven by an induction motor is increased, rotor speed____

decreases

when the physical load driven by an induction motor is increased, synchronous speed ____

stays the same

when the physical load driven by an induction motor is increased, torque___

increases

when the physical load driven by an induction motor is increased, slip___

increases

when the physical load driven by an induction motor is increased, rotor current ___

increases

when the physical load driven by a synchronous motor is removed, rotor speed___

remains the same

when the physical load driven by a synchronous motor is removed, synchronous speed___

stays the same

when the physical load driven by a synchronous motor is removed, torque___

decreases

when the physical load driven by a synchronous motor is removed, slip___

stays the same

when the physical load driven by a synchronous motor is removed, rotor current___

decreases

three classifications of stator wound DC motors

shunt, series, compound

_____ is a measure of the force that creates a spin or rotation on the axis of a motor

torque